The toolbar's core functionality comes from the community of people that use the toolbar. People report phishing sites using a feature of the toolbar or by filling in a form at the Netcraft Web site. Netcraft validates the reported sites and builds a database that is used by the toolbar to block access to those sites, which effectively prevents people from inadvertantly visiting a site that might be used to steal private information.
The toolbar is freeware and available for anyone to use. Netcraft also provides a paid service, Phishing Site Feeds , which lets businesses easily integrate the same database used by the toolbar into their content filtering systems. The database, which as of April 2005 contained more than 5400 phishing sites, can be integrated with a mail server, Web filtering system, firewall, intrusion detection systems, etc.